In a patient with questionable leukemia and low white cell count, which procedure is least likely to be informative?

In the context of a patient with questionable leukemia and a low white cell count, the procedure that is least likely to be informative is a PHA-stimulated blood culture.

PHA, or Phytohemagglutinin, is a plant-derived lectin that is used to stimulate lymphocytes in culture, promoting cell division and proliferation. This process relies on the presence of adequate numbers of activated white blood cells to yield meaningful results. In a situation where the patient has a low white cell count, there may not be enough viable lymphocytes available to respond to the stimulation by PHA. Consequently, the culture could fail to produce satisfactory growth of cells, limiting the ability to assess clonal abnormalities that may indicate leukemia.

In contrast, an unstimulated blood culture might still yield some viable cells, albeit in a less dense population, allowing for certain assessments. Q-banding involves banding techniques that utilize Giemsa staining to provide a cytogenetic profile, and FISH (Fluorescence In Situ Hybridization) can target specific chromosomal abnormalities with high sensitivity, even in small cell samples. These techniques do not depend primarily on the proliferation of cells, making them more reliable under conditions of low white cell count. Hence, the